PC users have until Friday to scan their computers for a highly destructive virus which is spread through pornographic email attachments.

If the Nyxem-E virus is not removed, it will delete Word, Powerpoint, Excel and Acrobat and other common files on infected machines.

The virus, which is also known as MyWife, Blackworm, Kama Sutra, Grew and CME-24, first appeared on 16 January. It arrives in emails with attachments promising porn videos and pictures.

Once downloaded on to a PC, the virus self-replicates by harvesting email addresses and sending itself on. It will also seek out any vulnerable computers on a shared network.
Nyxem is programmed to cause maximum damage by targeting 11 common types of file on the third day of every month.

It also attempts to disable anti-virus software to stop it updating and can also affect the mouse and keyboard on infected machines.

An estimated 300,000 machines worldwide are already infected.

Leading security software will protect computers against the virus as long as it is up to date.

PC users are being urged to update their anti-virus software and run a full disk scan.

If it is not cleaned out, the virus will continue to activate each month to repeat the problem.AOL security expert Will Smith said: "It's almost impossible to tell if you have a virus like this, as it will sit dormant on your computer until activated.

"The best way not to get this virus is not to open any email attachments you suspect, but it’s also critical you have reliable, up-to-date anti-virus software.

"If you're in any doubt or you think you might be vulnerable, run a full virus scan of your computer before Friday to identify anything unusual on your PC."

Jason Steer, technical consultant at mail filtering firm Ironport, told Web site Computeractive that 99 per cent of consumers did not regularly back up their data or update their anti-virus software.

"We are seeing an upward trend in malicious emails. There are two reasons behind this. One is for criminal activities, others such as Nyxem are because the virus writers may be bored and doing it just because they can," he said.

"Consumers should ensure they keep their anti-virus software up to date and back up important documents to DVD or CD."